1. Field of the Invention
The present invention relates to a droplet-discharging-head manufacturing apparatus, a droplet-discharging-head manufacturing method, a droplet discharging head, a droplet discharging device, and a printing apparatus.
2. Description of the Related Art
A droplet discharging head provided in a droplet discharging device of an inkjet recording apparatus used as an image recording apparatus or an image forming apparatus, such as a printer, a facsimile machine, or a copying machine, includes a nozzle for discharging ink droplets; a pressurizing chamber (also referred to as an ink flow path, a pressurizing liquid chamber, a pressure chamber, a discharge chamber, or a liquid chamber) communicating with the nozzle; and a piezoelectric element that pressurizes ink in the pressurizing chamber. A voltage is applied to the piezoelectric element so as to generate energy through which a diaphragm is displaced to pressurize ink in the pressurizing chamber, thereby discharging ink droplets from the nozzle.
As the piezoelectric element, there are known types including a longitudinal vibration type using displacement in the d33 direction and a lateral vibration type (may be referred to as a bending mode) using displacement in the d31 direction. Of the above types, a thin-film piezoelectric element is known, in which a pressurizing chamber including a diaphragm is formed on a Si substrate, and a piezoelectric body of the lateral vibration type is directly formed on the surface of the diaphragm by using a semiconductor process or a micro electro mechanical systems (MEMS) technology so as to form high-definition images.
The piezoelectric element as described above is formed such that a constituent material having a ferroelectric property is deposited on a lower electrode on the surface of a silicon wafer by using a known film formation technology, such as various vacuum film formation methods, a sol-gel method, a hydrothermal synthesis method, an aerosol deposition (AD) method, or a coating-pyrolysis method, to form a ferroelectric layer with a desired thickness, and thereafter, an upper electrode layer is formed thereon. Then, the piezoelectric element is cut into a desired shape by using a lithography method or the like to form independent piezoelectric elements for respective pressurizing chambers. The silicon wafer on which a plurality of piezoelectric elements is formed is cut along a dicing line so as to be divided into a plurality of silicon chips. Thereafter, various processing processes are performed on each of the silicon chips to manufacture a plurality of droplet discharging heads.
The ferroelectric layer as described above is formed such that, for example, a ferroelectric precursor film that is a coating film made with a ferroelectric precursor (a liquid containing a constituent material having a ferroelectric property) is formed by the sol-gel method or the like, and thereafter a heating process (crystallization through baking) is performed (see, for example, Japanese Patent No. 3387380).
Japanese Patent No. 3387380 discloses a method in which a plurality of silicon wafers, on which ferroelectric precursor films are formed, is fixed on a fixing jig. In the method disclosed in Japanese Patent No. 3387380, the fixing jig is inserted into a diffusion furnace at predetermined velocity to perform a heating and baking process on the silicon wafers fixed on the fixing jig, so that a ferroelectric layer is formed. Thereafter, the fixing jig is discharged from the diffusion furnace.
However, if the manufacturing method disclosed in Japanese Patent No. 3387380 is used, heat (the thermal history) applied to each of the silicon wafers during the heating and baking process varies. Therefore, the thermal history of the ferroelectric layer of a piezoelectric element varies between the silicon wafers, so that displacement of a diaphragm due to the displacement of the piezoelectric element may vary. The variation in the displacement of the diaphragm may cause a variation in the discharging property of a droplet discharging head.
Therefore, a technology for preventing a variation in the thermal history of the ferroelectric layer between the silicon wafers is disclosed (see, for example, Japanese Patent Application Laid-open No. 2005-327920).
Japanese Patent Application Laid-open No. 2005-327920 discloses a technology in which a plurality of silicon wafers, on which ferroelectric precursor films are formed, are fixed on respective stages arranged in a row. In the technology disclosed in Japanese Patent Application Laid-open No. 2005-327920, the stages arranged in the row are inserted into a heating furnace in order from a stage on one end side and thereafter moved backward so as to be discharged from the heating furnace. Japanese Patent Application Laid-open No. 2005-327920 also discloses that the order of the stages is changed at every predetermined number of times.
However, in the technology disclosed in Japanese Patent Application Laid-open No. 2005-327920, the stages arranged in the row are inserted into the heating furnace in order from the stage on one end side and thereafter moved backward so as to be discharged from the heating furnace. Therefore, a staying duration in the heating furnace varies between a silicon wafer held by a stage that is firstly inserted into the heating furnace among the stages and a silicon wafer held by a stage that is lastly inserted into the heating furnace among the stages. Therefore, even when the order of the stages is changed, it may be difficult to prevent a variation in the thermal history of the ferroelectric film between the silicon wafers. Furthermore, the thermal history also varies between ferroelectric layers laminated on each of the silicon wafers.
Therefore, it is difficult to prevent a variation in the discharging property due to the variation in the thermal history of the ferroelectric layer between the droplet discharging heads.
The present embodiment has been made in view of the above and there is a need to provide a droplet-discharging-head manufacturing apparatus, a droplet-discharging-head manufacturing method, a droplet discharging head, a droplet discharging device, and a printing apparatus capable of preventing a variation in the discharging property between the droplet discharging heads.